1. Field of the Invention
The present invention relates to trailer hitches and, more specifically without limitation, to weight-distributing trailer hitches.
2. Description of the Related Art
Trailers, such as flat-bed trailers, horse trailers, and the like are commonly towed behind a towing vehicle. Such trailers generally have a forwardly-extending tongue with a hitch ball socket that is pivotally securable to a hitch arrangement mounted on the rear end of the towing vehicle. A weight-distributing hitch generally includes a hitch head with a hitch ball mounted thereon to matingly receive a hitch ball socket of the trailer. If the force at which the hitch ball socket bears downwardly against the hitch ball is excessive, sometimes referred to as tongue weight, the trailer tends to sway back and forth as the trailer is being towed behind the towing vehicle even along straightaways, commonly referred to as “porpoising”, which seriously jeopardizes the ability of the operator of the towing vehicle to reliably control steering and stability of the towing vehicle and the trailer, sometimes with disastrous results. Trailer swaying creates substantial discomfort and anxiety not only for the driver of the towing vehicle but also for drivers of oncoming, following, and passing vehicles as well as jeopardizes the safety of the contents of the trailer. Trailer sway arises from a variety of sources, such as cross-winds, rough and/or uneven road conditions, improper tongue weight without redistribution between the front wheels and rear wheels of the towing vehicle, etc. Trailer swaying can be described as simulated small alternating turns, first toward one side, then the other.
It is well known in the art that trailer sway may be partially reduced, but not eliminated, by distributing some of the tongue weight from the back wheels of the towing vehicle to the front wheels of the towing vehicle. Such tongue weight redistribution is typically accomplished by adjusting the tilt of the hitch ball in combination with adjusting the tension being applied to distal ends of opposing spring bars having proximal ends thereof pivotally secured to the hitch head.
Primary objectives of cooperatively adjusting the tilt of the hitch ball and the tensions in the spring bars include adjusting the hitch ball wherein the axis of the hitch ball is vertically-oriented, aligning the axis of the hitch ball socket of the trailer with the axis of the hitch ball of the weight-distributing hitch, leveling the elevation of the trailer tongue relative to the normal unloaded elevation of the hitch arrangement of the towing vehicle, and adjusting tensioning of the spring bars to more evenly distribute the tongue weight from the rear wheels of the towing vehicle to the front wheels of the towing vehicle.
Prior art weight-distributing trailer hitches utilize various mechanisms to adjust the orientation of the hitch ball axis and the elevation of the hitch ball. For example, U.S. Pat. No. 6,629,701 of Colibert, which disclosure is incorporated herein by reference in its entirety, includes a hitch head having a pair of shank mount plates and an adjustable hitch shank. Other prior art hitches utilize beveled cam discs to make tilting adjustments of the hitch ball; see, for example U.S. Pat. No. 3,801,133 of Thompson.
The proximal ends of the spring bars of prior art weight-distributing trailer hitches typically are journalled to pivot about opposing vertically-oriented axes spaced equidistantly and laterally outwardly relative to the hitch ball of the hitch head. Distal ends of the spring bars extend rearwardly along the right and left rails of the tongue of the trailer. A left lifting mechanism tensionally connects the distal end of the left spring bar to the left tongue rail of the trailer, and a right lifting mechanism tensionally connects the distal end of the right spring bar to the right tongue rail of the trailer.
The lifting mechanisms are spaced above the distal ends of the spring bars and apply upward tensioning to the distal ends of the spring bars to accomplish the desired weight-distribution of the tongue weight. As a turn to the left or a trailer sway toward the left occurs, the hitch ball socket of the trailer pivots clockwise relative to the hitch ball of the weight-distributing hitch. Simultaneously therewith, the lateral offsetting of the vertically-oriented pivot axes of the proximal ends of the spring bars causes the distal end of the right spring bar to be displaced forwardly with the result that the lower end of the tensioning chain on the outside of the sway is spaced forwardly from the upper end of the right tensioning chain, and causes the distal end of the left spring bar to be displaced rearwardly with the result that the lower end of the tensioning chain on the inside of the sway is spaced rearwardly from the upper end of the left tensioning chain. Any change in the horizontal component of the tension in the right chain arising from the sway to the left would be substantially equal and opposite to the change in the horizontal component of the tension in the left chain arising from the left sway. In other words, any moment created in the right chain that might have urged counterclockwise rotation of the hitch ball socket about the hitch ball to thereby counteract the sway of the trailer to the left is cancelled by an equal and opposite moment created in the left chain.
Various mechanisms have been utilized by prior art weight-distributing hitches to allegedly control trailer sway. For example, U.S. Pat. No. 6,629,701 of Colibert teaches the use of a sway control adjustment control plate fixed to the bottom of the hitch head to control trailer sway.
For another example of a weight-distributing hitch for allegedly controlling trailer sway, see U.S. Pat. No. 5,984,341 to Kass et al., which teaches the use of friction pads, namely adding additional elements which are exposed to the elements and are inherently subjected to substantial wear, tear and contamination but, unfortunately, only minimally reduce swaying, if any, while also inhibiting the trailer from quickly and reliably returning to a non-sway equilibrium configuration.
As yet another example of a prior art weight-distributing hitch that allegedly controls trailer sway, see U.S. Pat. No. 6,419,257 to McCoy et al. which teaches the use of cams and cam followers for that purpose. During a sway to the left, the lateral offset of the pivoting trunnion of the left spring bar displaces the distal end of the left spring bar rearwardly which causes the concave-downwardly cam follower to ride upward onto the cam thereby increasing the tension in the chain of that lifting mechanism. Simultaneously therewith, the lateral offset of the pivoting trunnion of the right spring bar displaces the distal end of the right spring bar forwardly which causes that concave-downwardly cam follower to also ride upwardly onto its cam thereby also increasing the tension in the chain of that lifting mechanism. In other words, the increased tensioning in the opposing lifting mechanisms cancel out any anticipated moment for controlling trailer sway. Similar circumstances apply when the trailer sways to the right.
What is needed is a weight-distributing hitch that controls sway by increasing tension in a spring bar disposed toward the outside of a sway while simultaneously decreasing tension in an opposing spring bar disposed toward the inside of the sway so the changes in the tensions of the opposing spring bars cooperatively and dynamically create moments which counteract swaying of the trailer by returning the trailer to an equilibrium configuration where the trailer is again aligned with the towing vehicle.
What is also needed is such a weight-distributing hitch that can also control sway without requiring any additional parts, such as sway control plates fastened to the hitch head, friction pads, cams and cam followers, etc., particularly since the amount of access generally available for weight-distributing hitches is very limited due to the minimal available space on the trailer tongue sometimes being needed for other purposes, such as cover plates, propane tanks, tool boxes, and other necessary equipment.